Air brake



Aug. 13, 1935. c. A. CAMPBELL 2,010,914

r AIR BRAKE VFiled July 27, 1932 2 Sheets-Sheet l Aug. 13, 1935.

A. CAMPBELL AIR BRAKE Filed July 27, 1952 2 sheets-sheet 2lllllllllllllll/ :'l/Illllllll//l/ Snvento Patented Aug. 13A, 19352,010,914 i sin BRAKE Charles A. Campbell, Watertown, N.v Y., assignerto The New York Air Brake Company, a corporation of New erseyApplication July 27, 1932, Serial No. 625,098

22 Claims. (Cl.` 303-82)f `This invention relates to air brakes, andparticularly'to means for venting the brake pipe in service and inemergency and for preserving such a definite distinction between the twotypes of venting thatan application which is initiated by a servicereduction shall never degenerate into an emergency application. ,Anotherand related feature of the invention is stabilization of the emergencyvalve against functioning as the result 1o` oi overcharging of thebalancing chamber.

The increasing length of trains has led to a demand for more rapidpropagation of service applications. This entails sharperand more in.tense service venting with an increased tendency 15: toward undesiredemergency applications.

i The invention is applicable with any quick service venting mechanismin which a substantially uniform amount of air is discharged from thebrake pipe in each quick service function. A separate emergency'ventvalve is used and is of that `vvell known type inwhich the emergencypiston is interposed'betvveen the brake pipe and a balancing chamber. Asheretofore, the emergency piston controls the charging of the balanc`ing chamber from the brake pipe under running conditions and controlsthe bleeding of the balancing chamber to the brake pipe at a servicerate when the piston moves under a service reduction of brake pipepressure to a service position in 3o; which it is ready to actuate butdoes notactuate the emergency vent valve. Where `local quick serviceventing is not intense this bleeding flow from the balancing chamber issuiicient to arrest the emergency piston in service position before itacts to open the emergency vent valve, but it has been foundinsuiiicient Where intense service venting is used.

The present invention contemplates increasing the lost motion travel ofthe emergency piston from running position to the position which itassumes in service so that the pressure in the balancing chamber will bereduced quite substantially by such motion. Y i

Assuming that quick service venting does reduce brake pipe pressure adefinite amount, the displacement oi the emergency` piston in movingirom running to service positionsis so coordinated `with the volume of`the balancing chamberthat balancing chamber pressure drops to anequality or substantial equality with brake pipe pressure, The relationneedinot be precise, but the effect is to dissipate by expansion inthebalancing chamber, pressure which 'might force the "emergency piston farenough to open the emergency vent valve, Where a measuring chamber isused with the quick service valve, the invention contemplates-coordination of the volumes of the measuring chamber, thevolume of thebrake pipe on the corresponding car, the volume of the balancingchamber, and the emergency piston displacement in moving idly fromemergency to service position. 1 i

Various quick service mechanisms are known,

some of which are independent of the triple valve,

and others of which form a component part of the triple valve. Eithertype maybe used. While I prefer to make use of a measuring chamber to ycontrol the service venting, because of its more precise action, controlof service venting may be secured by other means'and if effective, wilisumce ior embodiment according to the invention. L

The invention attains its greatest usefulness in connection with a quickservice venting mechanism o" the so-called repeater type, i. e., onewhich vents the brake pipe on each successive reduction of brake pipepressure in a split reduction application, but it may be used with quickservice mechanisms of the non-repeating type;

Where a measuring chamber is used, the distinction between the two typesturns on whether the chamber is Vented in lap position (repeating type)or is not vented until the valve moves to release position(non-repeating type). By giving the emergencyrpistonsa substantial falsemotion b toa release position from normal running posi,- tion anovercharge of the balancing chamber built up in release may bedissipated when the piston returns to running position.

While thel invention is applicable with many elaborate forms of triplevalveY having such well known characteristics as restricted release andrecharge, and the control of the development of brake cylinder pressurein service or in emergency, or both, these functions `are not involvedin the venting of the brakepipe either in service or in emergency andaccordingly, in the interest of a simple explanation, I shall describethe in; vention as applied to a very simple form of triple valve havinga quick service measuring chamber with means to vent the chamber duringrelease. As a modification I shall show the use of tvvol vent valves,one for service and the other for emergency venting, each independent ofthe triple valve. i

in the drawings:-

Fig. l is a vertical'axial section' through a quick service triple Valveand an emergency vent valve, coordinatedaccording to the presentinvention. The triple `Valve is in release and recharge position and theemergency valve is in running position.

Fig. 2 is a fragmentary View showing the triple slide valve andgraduating valve in service posi- Lion.

Fig. 3 is a similar view showing preliminary lap position.

Fig. 4 is a similar View showing emergency position.

Fig. 5 is a view illustrating a modied arrangement in which a brakepipe, plain triple valve, auxiliary reservoir and brake cylinder (allshown in elevation) are connected with a quick service vent valve and anemergency vent valve v(both shown in vertical axial section) the twovent valves being coordinated according to the present invention.

In the drawings ii represents the bracket having a mounting flange i2.The brake pipe is shown at i3 and is connected to a branch pipe ifiwhich is connected with the bracket il. An auxiliary reservoir (notshown) is connected to th'e bracket by the pipe i5, and the brakecylinder (not shown) is connected with the bracket by pipe i6. Thebracket l i is formed with two mounting faces against one of which isbolted the body ll of the triple valve, This triple valve has a slidevalve chamber i8 and a cylinder i@ for the triple piston 2i. The triplepiston controls charging flow through the charging groove 22. In releaseposition it seats against the iiange 23 at the outer end of the slidevalve chamber i3, charging flow occurring through slot E.

The pistonl has a stem 25 which is guided at its inner end by a spider26. The stem 25 also has a collar 2l and between the collar 2l andspider 26 a slide valve 28 is confined, but is permitted a limitedamount of lost motion. The valve 28 coacts with a seat formed in thelower part of the valve chamber i8. There is a graduating valve 29mounted on a seat on the upper face of the valve 28, the valve 29 beingclosely confined in a notch in the stem 25. It thus moves with thepiston 2l and is moved relatively to the Valve 2S as a result of thelost motion permitted the latter.

The valves 28 and 29 are held to their seats by the usual bow-springswhich are indicated in the drawings. The iront cap 3i is of familiarform and is sealed to the body il by means of a gasket 32 which alsoserves as a seat for the rim of the piston 2i in the emergency positionofthe latter. A threaded plug 33 serves as a seat for the graduatingsprings 3l?- and 35 which position graduating stops 35 and 3? designedto coact serially with the piston 2i, the stop S being slidable in thestop 3l.

The branch pipe i4 leading from the brake pipe communicates Aby way ofpassage 35 with the space to the leitof piston 2i. Formed in the lowerpart of the body Il is a chamber 39 which is the quick service measuringchamber. A port 4l, called the quick service chamber port, is formed inthe seat for the slide valve i8. A quick service brake pipe port 42 isalso formed in this seat, as are the exhaust port 33 and the brakecylinder port fli. The port d3 leads to atmosphere, and may becontrolled by a retainer. as usual, if desired. The portii-icommunicates with the brake cylinder pipe l There are two ports d5and i8 which lead through the slide valve 23 from top to bottom. Inservice position these two ports register with the ports 42 and di andat such time are connected by the recess l in the graduating valve Z9.There are three ports in the lower farce of the slide valve 28, namely,58, IBS and 5l. These are oonnected together and are also connected to aport 52 which leads to the upper face of the valve. In release positionport 58 registers with il and port 5l registers with port IM, while theport 139 registers with the exhaust port 23. Consequently in releaseposition the measuring chamber 3S and the brake cylinder are bothexhausted.

There is a port 53 which extends through the slide valve 28 from top tobottom. In service position this registers with the brake cylinder portfiat. Its upper end has a restricted extension 5d and is controlled bythe graduating valve 29. Consequently when the graduating Valve moves tothe right from service position spring 34 assists until valve 29 lapsthe upper end of the port 53 but does not terminate service flow sinceextension Effi is still open. Gradual fall oi auxiliary reservoirpressure causes the iinal lapping motion. In service position the port3S is moved out of register with port il and port 5l is moved out ofregister with port dll. In service position the port 3S registers withport M and port i5 registers with port 52. Ports i5 and 12S areconnected at such time by cavity fil causing quick service ow to chamber39.

The novel features of the triple valve above described form the subjectmatter of my prior application, Ser. No. 5 3,635, filed Feb. 17, 1932,and hence these features are not claimed in the present application.

Mounted against the second mounting face described as formed on bracketi l, is the upper case di of the emergency vent valve. This is open atthe top, the opening being closed by cap 6?. which serves as a springseat for the emergency vent valve spring 53. The spring S3 reactsdownward against the emergency vent valve 54 which is of ordinary formand closes against a seat t5 with which it seals by means of an insertedface BG of rubber or other suitable material.

The chamber 5l within the body 6! is in direct communication with thebrake pipe by means of a branch passage leading from pipe i4 through thebracket l i. Flow through the seat passes to atmosphere through a Ventpassage 68. The cap $2 is sealed to body 6i by means of a gasket and thebody 6l like the body il, makes a tight joint with its mounting face onthe bracket Il by means of an appropriate ported gasket.

Suspended beneath the body Si is a cup-like shell il@ which encloses thebalancing chamber H and has removably mounted within its upper margin abushing 'iii for the emergency piston i3. The shell 89 and bushing l2seal to the body Si by means of a gasket as shown. Piston 713 has acup-like depression 'M at the center of its upper face and mounted inthis isa coil compression spring the upper end of which is centered by astud formed on the lower face or" the body il as shown.

Projecting downward from the piston "e3 is a guide stem 56. This worksloosely in a guideway formed in bushing ll which is threaded into thecup-like hub 'i3 suspended from cylinder bushing 'l2 by arms 39. Guidedin hub 'E3 is a sliding stop 8S urged to its upper limit of motion byspring 3?.. In its normal position stop 8i arrests piston 'i3 in itsnormal or running position. Ir" it yields under high releasing pressurepiston 'i3 may move down until its gasket 83 seats cn rim S4 formed incylinder bushing l2. In this position, called release position, chargingow is limited strictly to thecapacity or side port 85 leading from thebore Bin stem.` and the clearancebetween stem 16 and guide bushing 1T; 1

The piston 'I3 carriesva `plurality of upstanding thrust pins 81, two ofwhich appear in the drawings, which pass through a passage ofsubstantially greater diameter formed in the body 8l; and have reducedportions passing' through valve 54 and having shoulders 88 in positionto strike the valve and unseat it after `limitedlupward travel of thepiston. VThe passages around the stems 8l provide for directcommunication between the chamber 67E, which is the brake pipe chamber,and the space above the piston 13.

The balancingchamber 'H is charged by flow through these passages,thencethroughpassage 85 and lateral passage S5 and through the clearanceinthe guideway to the chamber 1l. When brake pipe pressure is reduced ata service rate, the piston moves up until the shoulders 88 on pins 81engage the valve $4 without opening the valve. This iscalled serviceposition.

The novel mechanical features of the vent valve above described form thesubject matter otrny prior application Ser. No. 563,619, led Septemberi8, 193i, and hence are not claimed in the present application.

The motion of the piston 'I3 from running position, shown in thedrawingsto service position in which the shoulders 88 engage valve E4without unseating. the valve, is somewhat greater than is customary, andaccording to the invention the displacement of piston 1.3 in the idlemotion just described, is so coordinated to the total volume oi chamber'il that such upward motion of the piston will reduce the pressure inchamber H by substantially the same amount. that brake pipe pressure isreduced by connection of the brake pipe with the chamber 39. Thiscoordination can be readily carried out for `the reason that the brakepipe has a definite volume on each car and the measuring chamber 39 onthat car can be made'to correspond.

. @In emergency valves of the type here described,

as heretofore constructed, back flow through the port and passage 8E ata ratecontrolled by the size of the port 85, was reliedupon to dissipatepressure from the chamberll and prevent the piston from unseatingthe-emergency valve.` That action is present in the i valve heredescribed, but is supplemented by the marked depletion of pressure inthe balancing chamber 'i l which arises from the lost motion travel ofthe piston T3.

The piston i3 will movefromnormal orrunning position to the so-calledrelease or lowermost position rinlyin response to an excessive releasingpressure in the brake Vpipe,such as occurs at the head end of trains. Insuch release position the sealing of gasket. 83 resists overcharge butdoes not prevent it. Thetravelbetween release and running positions ismade longer than usual and is so coordinated. with the area of thepiston and the volume of chamber 1I that motion back to running positionwill dissipate the ovcrcharge in 'H by expansion. Hence undesiredemergency action as the result .of overcharges is avoided.

`The function of spring 'i5is to ensure that the piston moves fromservice to running position. Omission or" the spring is possible. Thegroove 89 may be used if desired to ensure closing of valve 64 beforethe brake pipe is completely exhausted. Piston 'i3 opens port 88 inemergency position and vents chamber H at a moderatelyrapid rate.

ervoir` is charged in the usual manner. The brake cylinders' are`exhausted to atmosphere and the measuring Vchamber 3S is exhausted toatmos- YThe balancing chamber 'I I. is charged.

phere.

Service position Upon a service reduction of brake pipe pressure, thepiston 2l moves outward to quick service position. So tar as quickservice venting is concerned it suffices to say that the brake pipe isconnected to the chamber 38 so that pressures in the chamber and brakepipe equalize producing a denite reduction of brake pipe pressure. Inresponse to this reduction, the piston 13 moves upward until it engagesthe valve 64 without opening the latter. Because of the coordination ofvolumes, already described, the pressure urging piston I3 upward isreduced at this point to substantial equality with reduced brake pipepressure. Consequently there is no tendency for the emergency piston toovertravel and cause an undesired emergency application.

S ervzce lap position used) whereupon the spring 'l5 will restore thepiston 13 to running position. Under these conditions'brake pipepressure and pressure in the chamber 54 are again equal. A secondreduction of brake pipe pressure will repeat the functions alreadydescribed.

Emergency On an emergency application a rapid reduction of brake pipepressure causes the piston I3 to move upward to its limit of motion,unseating the valve Eli and venting air from the brake pipe directly toatmosphere. l Y

General conszderctio'risA It is not strictly necessary to use the spring5, and ordinarily this spring would be light. When the spring ispresent, the pressure in chamberii'tl, when the piston first arrives inservice position, is necessarily slightly higher than it is when thespring is omitted, but the principle is the same in both cases. In fact,it is not necessary thatl the coordination of brake pipe volume, quickservice measuring chamber volume, balancing chamber volume, andemergency piston displacement, be precise. It is possible bycoordination of these volumes, according to the principles above setforth, so to stabilize the emergency valve that it will not respond to aservice reduction of brake pipe pressure even though the local serviceventing be quite pronounced and sudden. The suddenness of the serviceventing is highly important to rapidpropagation and heretoforesuddenlventing was extremely likely to cause a sensitive emergency'valveto move to emergency position because it allowed no adequate time forCII back flow to occur through vthe ports and 86. According to thepresent invention this back iiow is not essential to dissipate thepressure which forces the emergency piston 7|3'from running to serviceposition and which if not'dissipated would cause this piston to continueto emergency position. The motion of the piston itself eiects thedesired result, and then equalizing fiow through ports 85 and Semodified by the action of the spring 'i5 (if used), restores theemergency valve to running condition ready to repeat the function justdescribed, or to move to emergency position upon an ensuing reduction ofbrake pipe pressure. A similar result is secured when piston 'I3 movesfrom release to running position. The eiect is to permit the use ofextremely sensitive valves with no danger of aceidental functioningunder conditions which would cause prior valves to function falsely.

The particular type of triple valve with which the arrangement is usedis immaterial. The quick service vent may or may not be embodied as acomponent part of the triple valve. To illustrate this possibility aswell as other optional features, Fig. 5 has been included in the presentdisclosure.

Referring to Fig. 5, 9| represents a mounting bracket with supportingange S2, to this is connected a branch 9e from the brake pipe 93. Frombranch gli a pipe $25 leads to bracket S5 on which is mounted a triplevalve 6l! of the pipeless type. A brake cylinder 98 and auxiliaryreservoir 99 are piped to bracket 96 which establishes properconnections between triple valve, brake pipe, brake cylinder andauxiliary reservoir. The triple valve Sl has no service or emergencyventing functions but merely controls admission and exhaust of air toand from the brake cylinder and the charging or" the reservoir (of whichone or more may be used as is well known in the art).

rThe bracket Si is formed with a cross passage it with which brake pipebranch te communicates. Passage IEM terminates in two opposed mountingfaces, one for a quick service vent valve and the other for an emergencyvent valve. Formed in bracket 9| is a small measuring chamber I 92 forthe quick service vent valve and a large measuring chamber |93 for theemergency vent valve. These are isolated from each other and frompassage le I. Each has a restricted vent to atmosphere, chamber |il2through an interchangeable choke leli and chamber |533 through aninterchangeable choke |05.

The emergency vent valve is identical with that already described withone exception. The pasv sage E53@ leads to chamber |93, unlike passage68 of Fig. 1 which leads to atmosphere. This is the sole difference.Identical parts are indicated by the same numerals Si to '67 inclusiveand S9 to B inclusive '(used on Fig. 1). Chamber tl communicatesdirectly with brake pipe passage lill.

Functionally a slight diierence is introduced by the use of chamber |93and choke IE5. Groove 88 is of such capacity that pressure in chamber'II falls in emergency at a rate slower than the fall of brake pipepressure caused by initial flow to chamber w3, but faster than brakepipe pressure is lowered by flow through choke |635 after chamber |93 ischarged. Hence emergency venting is limited to little more than thecapacity of chamber |53.

The quick service vent valve is provided with a body IGS having achamber IM in direct cornmunication withl brake pipe passage I GI and avent passage |08 in direct communication with quick service chamber |02.f

The outer end of body |06 is apertured to receive a exible diaphragm|09, which is clamped at its margin by a cap I I I. This encloses achamber |I2 to the left of the diaphragm H39. The diaphragm H29 isclamped at its center between two convex discs ||3 and H4, the first ofwhich is integral with a stem |65. Stem H5 is guided at M5 in body |05and in sleeve |I'I in cap I|I. A nut I I8 threaded on the stern clampsthe discs together. The margins of the discs serve as limit stops inconjunction with portions of housing |96 and cap II and are notched toassure free air flow.

The chamber I I 2 is charged from the chamber I 'I through a port I I9which leads to the end of guide sleeve IE'I. The stem H5 is bored fromits outer (left) end at I2|, and from bore |21 lead two lateral ports, asmall one |22 which is always open to chamber I |2 and a larger one I 23which is blanked by sleeve II'i when diaphragm |09 is in its outer (lefthand) position, and which is exposed when the diaphragm is in its innerposition.

Thus chamber I I2 which is a balancing chamber or reservoir is chargedfrom the brake pipe at a rate determined by the flow capacity of port|22, and discharges back to the brake pipe, when brake pipe pressure isreduced, at a rate xed by the combined flow capacity of ports |22 and|23.

The end of stem I I5 is in thrust relation with one end of lever |24which is fulcrumed at |25. The other end of levei` |24 is forked and isin thrust relation with cup |26 which in turn encircles pin valve I2?and is in thrust relation with collar |28 thereon, so as to be capableof drawing the valve open. The cup |26 is slidably guided in body It. Acoil compression spring 29 reacts against collar |28 and urges valve|2`| closed.

The valve |2'i coacts with a seat bushing ISI sealed in body |06 bythreaded plug |32 and controlling low from chamber |81 to port |68 an'dchamber I U2.

OPERATION or FORM SHOWN 1N FIG. 5

The functions of the emergency vent valve have been already described.

During release, the chamber |52 is charged as explained, the chargingrate being limited to the capacity of port |22.

On occurrence of a service reduction of brake pipe pressure diaphragm|09 moves to the right unseating valve |271 and exposing port |23.

Valve |27 has a capacity in excess of choke IM, so brake pipe pressureis reduced rapidly by flow to chamber |32, and then slowly at a ratedetermined by choke |6345. Since the flow capacity of choke IM is lessthan the combined flow capacity of ports |22 and |23 pressure in chamberH2 falls faster than brake pipe pressure once chamber H32 is charged.Hence valve |271 closes. Then choke |04 dissipates the charge in chamber|02.

Thus the service vent mechanism is conditioned to repeat its ventingfunction upon the next service reduction of brake pipe pressure.

The pressure drop produced by venting into chamber 232 causes piston 'i3of the emergency valve to move from running to service position and suchmotion produces a similar reduction of pressure in chamber 7|, so thatpiston 13 will not be moved beyond service position by quick serviceventing.

The adaptability of the invention to two different types of quickservice mechanism has been illustrated, any that gives a'measureddischarge might be used. One of the illustrated quick service mechanismsis of the repeating type. The other Amight readily be, since triplevalves of the repeating quick service type are known. The emergencyvalvehasbeenV shown as dissipating pressure in the chamber 'Il by twofunctionally different motions. VEither of these features may be usedindependently of the other. in the'claims the term piston isused in ageneric and not in a limiting sense. g

What is claimed is,-`

l. The combination of a brake pipe; a quick service vent valve having ameasuring chamber into which brake pipe air is discharged; and anlemergency valve comprising a balancing chamber and a Vent valveactuating `piston mounted between said balancing chamber and the brakepipe,

said piston `being aiorded a` definite amount of lost vmotion from itsnormal running position before it opens the emergency vent valve, the4volurne' oi the quick service measuring chamber being so coordinatedwith the brake` pipevolume f and the displacement of the emergencypiston `in its lost motion travel being so coordinated with thebalancing chamber volume, that the reduci tion of brake pipe pressureproduced by equalizaf l tion with the measuring chamber issubstantiallyl equal to the reduction` of` pressure in the balancing chamber producedbythe lost motiontravel v,of the emergency piston. Y

2. The combination of service vent .valve having a: measuring chamberinto which brake pipe air is discharged; andan emergency Valvecomprising `a balancing`cham r ifchamber, `said piston being afforded adeiinite amount of vlcst motion from its normal running GUY ber, a ventvalve actuating piston mounted be-` tweensaid balancing chamber -and thebrake A pipe, and a spring'iurging said piston toward said positionbefore it opens the emergency'ventvalve, the volume of the quick servicemeasuring chamber being so coordinated with the Abrake pipe volume andthe displacement of the-emergency piston in its lost motion travel beingso coordinated with the balancing `chamber volume, that the reduction ofbrake pipe pressure produced by equalization with themeasuring chamberis subi stantially equal to the reduction of pressure in the balancingchamber produced by the lost fmotion travel of the emergency piston. y 1

3. The combination of a brake pipe; a quick service vent Valvecomprisinga measuringchainber and pressure actuated means responsive toa service reduction of brakerpipe pressure to connect the brake pipewithsaidmeasuring chamber; and an emergency yalvecomprisingwaibrake pipevent valveya` balancingchamber charged from vthe brake pipes and a ventvalveactuating piston interposed `betweenthe` brake jpipe Vand saidbalancingchamber, said piston having-a definite `lost motion. travellfrom its normal;` runel ning position toV r 4 l mences to open theVemergency :vent valve the volume of ,ther quick ,service measuringchamber being -so' coordinated with` brake `pipe volume and thedisplacement of` the emergency Apistonin its. lost motion` travel beingso `coordinated with the balancing chamber'volume thatitheureduction ofbrake piperpressure occasioned `by connection with the `measuring -Kchamber `approxima.tes the reductionof balancinggchamber Vpressure.Soc-.

casioned by the lost Ymotion travel of the emergency piston. 1

a brake pipe; 't a i quick t 4. Thecombination of a ,brake pipe; aquickservice vent valve comprising a measuring cham' ber and pressureactuated means responsive to a service reduction of brake pipe pressureto connect the'zbrake pipe with said measuring cham-V fr ber; andanemergency valve comprising a brake pipe vent valve; a balancing chambercharged from the brake pipe,` a vent valve actuating piston 'interposedbetween the brake pipe and said balbeing so coordinated with brake pipevolume and the displacement ci theemergency pistcnin its lost motiontravei being so coordinated with the balancing chamber volume that thereduction of brake pipe pressure occasioned by connection with themeasuring chamber approximates the reduction of balancing chamberpressure occasioned bythe lostmotion travel of the emerA gency piston.

5. The combination of a brake pipe; a quick service vent valve`responsive to a service reduction of brake pipe pressure, and servingin re-V spense to such reduction to reduceA brake pipe 4pressure adefinite amount; an emergency vent valve; a balancing chamber; and apiston intere posed between the brake pipe and said balancing chamberand having a running position and a service positionto which it moveswith definite lost motion, and from which further movement serves tcopen the emergency vent valve, the displacement of the emergency pistonin its travel from running position to service position being socoordinated with the volume of the balancing chamber that balancingchamber pressure fallsl as a result of such travel of the piston insub-- stantially the same degree that brake pipe pres-` sure is reducedby said quick service vent valve.

6. The combination of a brake pipe; a-quick service vent valvelresponsive to a service reduction of brake pipe pressure, and serving inresponseto such reduction to reduce brake pipey pressure a definiteamount; an emergency `vent valve; a` balancing chamber; a` pistoninterposed betweenthe brake pipe and said balancing cham-J ber, andhaving a running position in which it controls charging flow tothebalancingchamber, and a service positiontowhichit`moves with definitelost motion and in which'it vents `the balancing chamber to thebrakepipe at a service rate and from which further movement serves toopen `the emergency vent valve; and a` spring urging said emergencypiston toward its ruiming positien; the displacement of the emergencypis. ton in itsftravel from `running position to` service positionbeing'so coordinated with the volume of thebalancing chamber thatbalancing chamber pippe pressure is reduced by` s aid quick service ventvalve. f

7. The combination `of, claim 5, further chare. acterized in that thequickfservicevent valve is of atypeadaptedto reduce the brake pipepresel sure by substantially uniform amounts' ineach of a plurality ofsuccessive brake pipe reductions.

A 8; The combination of Vclaim'3, further charac-v terizedin thatthequick service vent valve is of the repeating type.,` i

9. The combination of a brake'pipe;V 'a triple valve having a-cquickservice position iny which it reduces brake pipe vpressurea deniteamount by venting brake pipe air; and an emergency vent valve alsoconnected to the brake pipe and comprising a vent controlling valve, abalancing chamber, and a piston. interposed between the brake .pipe andsaid balancing chamber and movable by preponderant balancing chamberpressure upon reduction of brake pipe pressure through a denite lostmotion toV a position from which further motion will open said valve,the volume of said balancing chamber being so coordinated with thedisplacement of the piston in its lost motion travel that such motionWill reduce balancing chamber pressure substantially the amount thatbrake pipe pressure is reduced by quick service venting.

1).Y The combination of claim 9, further characterized in that thetriple valve includes a measuring chamber into which air is vented inquick service.

l1. The combination of claim 5, further characterized in that the quickservice vent valve includes a measuring chamber in constant restrictedcommunication with atmosphere.`

12. The combination of a brake pipe; a triple Valve-having a quickservice position in which it reduces brake pipe .pressure a deniteamount by venting brake pipe air; and an emergency vent valve alsoconnected with the brake pipe and comprising'a vent controlling valve, abalancing chamber, a piston interposed between the brake pipe and saidbalancing chamber and movable by preponderant balancing chamber pressureupon reduction of brake pipe pressure through a definite lost motion toa service position from which further motion will open said emergencyvent valve, and means actuated by said piston for controlling thecharging of said balancing chamber from the brake pipe, and the bleedingof said balancing chamber to the brake pipe in service position, thevolume of said balancing chamber being so coordinated with thedisplacement of the piston in its lost motion travel, that such motionwill reduce balancing chamber pressure substantially the amount thatbrake pipe pressure is reduced by quick service venting.

13. The combination of a brake pipe, a triple valve having a, quickservice position in which it reduces brake pipe pressure a definiteamount by venting brake pipe air; an emergency vent valve also connectedwith the brake pipe and comprisingl a vent controlling valve; abalancing chamber; a, piston interposed between the brake pipeand saidbalancing chamber and movable by preponderant balancing chamber pressureupon reduction of brake pipe pressure through a denite lost motion to aservice position from which further motion will open said emergency ventvalve; means' actuated by said piston for controlling the charging ofsaid balancing chamber from the brake pipe and the bleeding of saidbalancing chamber to the brake pipe in service position; and a springurging said piston toward Y said balancing chamber, the volume of saidbalancing chamber being so coordinated with the displacement of thepiston in its lost motion travel, that such motion will reduce balancingchamber pressure substantially the amount that brake pipe pressure isreduced by quick service venting.

14. .The combination of claim l2, further characterized in that thetriple valve includes a measuring chamber into which quick service airis vented in quick service. Y

15. The Vcombination of a brake pipe in which a normal pressure ismaintained under running conditions, and in which an excess releasingpressure is at times developed; a valve controlling venting flow fromsaid brake pipe; a balancing chamber; a piston interposed between saidbalancing chamber and said brake pipe, and controlling the charging ofthe chamber from the brake pipe in running position and the bleeding or"said chamber when brake pipe pressure is reduced at a slow rate, andserving to open said valve when brake pipe pressure is reduced at arelatively rapid rate; and a yielding stop serving normally to arrestsaid piston in running position but capable of yielding under saidreleasing pressure to permit the piston to move toward said chamber, thedisplacement of the piston in so moving, being so coordinated with thevolume of said chamber and the normal and excess brake pipe pressures,that returnof the piston by said stop to running position dissipatesexcess pressure in said chamber.

16. The combination of a brake pipe in which a normal pressure ismaintained under running conditions, and which is subject to pressureincreases for releasing brakes, and to deiinite quick servicereductions; a valve cont'roliing emergency venting dow from said brakepipe; a balancing chamber; and a piston interposed between said brakepipe and said chamber and controlling the charging and bleeding oi" thelatter, said piston having a normalruiming position from which it movesidly toward said chamber to a release position, and from which it movesidly away from said chamber to a service position in whichV it is aboutto open said vent valve, the displacement of the piston in so movingbeing so coordinated with the volume of said chamber and the releasingincrease and quick service reduction of brake pipe pressure, that excesschamber pressure is substantially dissipated by motion from release torunning position, and chamber pressure falls to substantial equalitywith brake pipe pressure in quick service.

17. The combination of a brake pipe in which a normal pressure ismaintained under running conditions, and which is subject to pressureincreases for releasing brakes, and to-denite quick service reductions;a valve controlling emergency venting ilow from said brake pipe; abalancing chamber; a piston interposed between said brake pipe and saidchamber, and controlling the charging and bleeding of the latter, saidpiston having a normal running position from which it moves idly towardsaid chamber to release position, and from which it moves idly away fromsaid chamber to a service position in which it is about to open saidvent valve, the displacement of the piston in so moving being socoordinated with the volume of said chamber and the releasing increaseand quick service reduction of brake pipe pressure, that excess chamberpressureY is substantially dissipated vby motion from release to runningposition, and chamber pressure falls to substantial equality with brakepipe pressure in quick service; and a yielding stop for arresting saidpiston in running position but capable of yielding to Apermit it to moveto release position.

`18. The combination of a brake pipein which a normal pressure ismaintained under running conditions, and which is subject to pressureincreases for releasing brakes, and to denite quick service reductions;a valve controllingemergency venting flow from said brake pipe; abalancing chamber; a piston interposed between'said brake pipe and saidchamberA and controlling the charging and bleeding of the latter, saidpiston having a normal running position from which it moves idly towardsaid chamber to a release position, and from which it moves idly awayfrom said chamber to a service position in which it is about to opensaid vent chamber pressure is substantially dissipated byA motion fromrelease to running position, and. chamber pressure falls to substantialequality with brake pipe pressure in quick service; and a spring urgingsaid piston from service toward running position.

19. The combination of a brake pipe in which a normal pressure ismaintained under running conditions, and which is subject to pressureincreases for releasing brakes, and to definite quick servicereductions; c a vvalve controlling emergency venting iiow from saidbrake pipe; a balancing chamber; a piston interposed between n saidbrake pipe and said chamber and controli ling the charging and bleedingof the latter, said piston having a normal runningvposition from whichit moves idly toward said chamber to a release position; and from whichit moves idly away from said chamber to a service position in which itis about to open said vent valve, the displacement of the piston inso'moving being so coordinated wththe volume ofV said chamber and thereleasing increase and quick service reduction or" brake pipe pressure,`that excess chamber pressure lis substantially dissipated by motion fromrelease to running position, and chamber pressure falls to substantialequality with brake pipe pressure `in quick service; a

spring urging said piston from service to running position; and ayielding stop for arresting said piston in running position but capableof yielding to permit it to move to release position.

20. The combination o1 a brake pipe; a vent valve; a balancing chamber;an abutment interposed between said brake pipe and balancing chamber,and shitable upon reduction oi'brake pipe pressure to open said ventvalve, said abut-` ment controlling charging of the chamber from thebrake pipe, and bleeding of Vsaid chamber upon moderate reductions of'brake pipe pressure; a measuring chamber into which said vent valvedischarges, said measuring chamber having a restricted bleed port forventing the same;

and a bypass, between said balancing chamber and brake pipe, opened bysaid abutment in valve opening position, and providing a rate ofreduction of balancing chamber pressure slower than the initial rate ofbrake pipe reductionv through the vent valve and faster than the rate ofbrake pipe reduction through the restricted bleed port.

2i. in an air brake system the combination of a normally charged brakepipe; a quick service venting mechanism operable in response to a slightreduction of brake pipe pressure to vent the brake pipe and produce adenite rapid additional reduction of brake pipe pressure; an emergencyvent mechanism including a normally charged balancing chamber and brakepipe emergency venting means responsive to pressure diierentialsbetweenthe brake pipe and such balancing chamber, said emergency venting meanshaving two ranges of action the first range being in response to areduction not less than that produced by the functioning of the quickservice venting mechanism irrespective of the rate at which such servicereduction occurs, and ineffective to open the emergency vent, and thesecond range being responsive to a reduction of brake pipe pressuregreater than that ,produced by quick service venting and effective toopen the emergency vent.

22. In an air brake system, the combination of a normally charged brakepipe; a quick service venting mechanism operable in response to a slightreduction of brake pipe pressure to vent the brake pipe and produce adefinite additional reduction of brake pipe pressure; an emergency ventmechanism including a .normally charged balancing chamber and brake pipeventing means responsive to pressure differentials between the brakepipe and said balancing chamber, said lactuating means having an idle`travel from a normal running position when the chamber and the brakepipe by increasing the the balancing chamber. v

effective Volume of A CHARLES A. CAMPBELL.

